1. Field of the Invention
The present invention relates to a continuous-type blood pressure measuring apparatus, and particularly to such an apparatus which displays temporary maximum blood pressure before displaying proper and more accurate blood pressure at the end of each of continuous blood pressure measuring cycles.
2. Discussion of the Prior Art
There are known apparatus for continuously measuring blood pressure of a living body based on magnitude variation of heartbeat-synchronous pulses produced from the body. These apparatus include means for continuously detecting (a) Korotkoff sounds produced as pressure in an inflatable cuff set around a body portion of a subject is varied; (b) pulse wave (pressure oscillation) transmitted to an inflatable cuff; or (c) oscillation of the wall of an arterial vessel by utilizing Doppler effect. These apparatus are adapted to display maximum and minimum blood pressure at the end of each of continuous blood pressure measuring cycles. In other words, accurate blood pressure cannot be determined or displayed before a whole blood pressure measuring cycle is terminated, for example before pressure in an inflatable cuff whose level has been increased to a suitable upper level, is decreased to a suitable lower level. However, it is preferred that maximum blood pressure be displayed as temporary or estimated maximum blood pressure as early as possible prior to the end of each measuring cycle because the maximum blood pressure is more important information than other information concerning the blood pressure.
In the above background, it is proposed to determine temporary maximum blood pressure (hereinafter, referred to TMBP) at each of continuous blood pressure measuring cycles (hereinafter, referred to BPMC's) by selecting a pulse from heartbeat-synchronous pulses detected at a current BPMC which pulse corresponds to the TMBP, based on a maximum difference in magnitude between each pair of adjacent ones of the currently detected, consecutive heartbeat-synchronous pulses. In this case, however, the maximum difference, based on which the TMBP is determined, may be changed as the current BPMC is progressed. Consequently, TMBP, once displayed, may be changed to another TMBP in the course of detection of the following heartbeat-synchronous pulses during the current BPMC. Thus, the TMBP determined in the above-indicated manner is not reliable.